Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $67.92   10.520%   $75.0652   $75.07   $75.05   $75.10  
  Purchase #2 $157.46   12.708%   $177.47   $177.47   $177.45   $177.50  
  Purchase #3 $69.42   10.619%   $76.7917   $76.79   $76.80   $76.80  
  Purchase #4 $237.69   5.414%   $250.5585   $250.56   $250.55   $250.60  
  Purchase #5 $201.92   8.445%   $218.9721   $218.97   $218.95   $219.00  
  Purchase #6 $48.40   13.546%   $54.9563   $54.96   $54.95   $55.00  
  Purchase #7 $202.74   7.780%   $218.5132   $218.51   $218.50   $218.50  
  7 purchase totals = $985.55       $1,072.3270   $1,072.33   $1,072.25   $1,072.50